Drilling by the oil industry in Arctic offshore waters, typically from artificial gravel islands constructed to support such drilling activities, creates a need for pipelines from these offshore drilling sites to transport oil and gas to production facilities onshore. Conventional pipelaying techniques are extremely difficult to implement in the Arctic offshore area, due to several factors:(1) a variable shifting ice cover, which can damage floating vessels or prevent movement of such vessels during much of the year;(2) gouging of the seafloor by ice keels, which requires that pipelines be deeply buried to prevent damage; and (3) permafrost soil conditions, which can lead to pipeline failure due to loss of soil support under the pipeline. Pipeline construction from the surface of the ice during winter is treacherous and impractical, and the open water construction season in summer is both short and unpredictable.
Applicant is not aware of any prior art which, in his judgment as one skilled in the pipeline art, would anticipate or render obvious the novel pipeline construction technique of the present invention; however, for the purposes of fully developing the background of the invention and establishing the state of the requisite art, the following is set forth and incorporated hereinto: U.S. Pat. Nos. 2,706,616; 2,847,655; 3,817,345; 4,245,313; 4,319,240; 4,117,895; 4,221,503; 3,667,556; 3,260,318 and U.S. patent application No. 541,821 filed Oct. 13, 1983, now U.S. Pat. No. 4,492,276.